Abstract Equivalent-thickness conversion among metallic targets is important for vulnerability assessment and protection modelling, but conventional coefficients are often treated as material constants and seldom include fragment morphology. Penetration tests were conducted on 616 armor steel, Q235 steel, and LY12 aluminum alloy using steel spheres, tungsten spheres, and tungsten block fragments. A V50-based database was established, and failure mechanisms were examined from perforation morphology, exit-side SEM, and metallography. A semi-empirical ballistic-limit model was developed from key variables, with a residual correction term to describe the coupled deviation between fragment geometry and target response. The corrected model achieved a mean absolute percentage error of 7.91% and a coefficient of determination of 0.852. The conversion matrices show strong dependence on fragment type. For 616 steel converted to LY12 aluminum alloy, the coefficient increases from 2.50 for spherical fragments to 3.48 for tungsten blocks, giving a morphology-induced deviation of 39.03%. Thus, conversion should be defined by fragment type and target material rather than by a single material constant.
Abstract A new finite element (FE)-based approach for calculating crack-tip strain energy density factor (SEDF) named “element strain energy density factor (ESEDF) approach” was proposed. Mode I, mode II, mode III and mixed mode cracks in both 2D models and 3D models were analyzed. A da/dN-ΔS-R equation considering stress ratios was proposed for mode I cracks and a fatigue crack growth test was done. The results show that the ESEDF approach directly computes SEDF from FE results without assuming plane stress/strain or calculating stress intensity factors. It performs best for regular mode I/II cracks in 2D and 3D models, but is less accurate for complex mixed-mode, 3D mode III, surface-cracks and coarse-mesh cases, while remaining acceptable accuracy. The proposed da/dN-ΔS-R equation correlates fatigue crack growth rate with SEDF ranges considering stress ratios in mode I cracks for steels well.
Abstract Ensuring the structural performance of reinforced concrete beams strengthened with engineered cementitious composites (ECC) demands a reliable prediction of their load-carrying capacity. This task is complicated by the nonlinear interactions among material properties, geometry, and applied loads. This study introduces a rigorously validated dense neural network model tailored to accurately predict the load-carrying capacity of ECC-strengthened reinforced concrete beams, and provides a powerful data-driven tool for advanced structural design. A comprehensive database was assembled from published experimental programs and high-fidelity numerical simulations, which includes diverse beam geometries, reinforcement ratios, and ECC layer configurations. Among a suite of machine-learning techniques, the optimized dense neural network achieved superior predictive performance (R2 = 0.975, mean absolute error = 14.544, root mean squared error = 18.190), which outperforms linear, tree-based, and other nonlinear models. Sensitivity analysis revealed beam depth and ECC tensile strength as dominant drivers of load-carrying capacity, while ECC layer thickness exerted a comparatively minor influence. Importantly, the inherent strain-hardening capacity of ECC was shown to markedly enhance ductility, energy dissipation, and seismic resilience. These findings highlight the potential of artificial-intelligence-based approaches to restructure the design of ECC-strengthened reinforced concrete beams, informed performance-based seismic design, and guide the next generation of robust, high-performance concrete infrastructure.
Abstract The prism charge warhead can achieve a good balance between dense damage elements and reduced aiming time. However, the conventional fragment velocity theory can’t be directly applied to calculate the fragment velocity of polygonal charges, resulting in a lack of effective metrics to evaluate their lethality and to guide practical design. In this study, the configuration decomposition method was first used to quantify the distribution relationship between polygonal charges and sandwich charges, and a preliminary model was established. Secondly, through numerical modeling, the unknown function within the model was determined, and pulsed X-ray experiments were designed and executed. Finally, the accuracy and applicability of the established model were verified using the test results, publicly published test results, and additional numerical simulations. The study's numerical simulations show high precision, with an absolute error of <5.44%. The error of the established calculation model is controlled within 7.70%. This research can provide a reliable tool for designing and optimizing the power of prism charge warheads.
Abstract Modeling hydraulic fracturing requires capturing the interaction between fluid flow and solid deformation, which leads to complex crack patterns, especially in materials that are heterogeneous at a given scale. At the microscale, such materials can be described as multiphase media with distinct mechanical properties, where damage initiates and may be significantly affected by internal pressure. This work models pressure-driven fracture propagation in heterogeneous materials using a phase-field approach. Representative volume elements with random particle distributions are generated through a take-and-place strategy and subjected to tensile tests within a phase-field framework. Internal pressure is incorporated by coupling it to the gradient of the phase-field variable, enabling the simulation of pressurized crack propagation. A numerical study evaluates the influence of pressure magnitude and aggregate volume fraction on the fracture response. Results demonstrate the ability of the approach to reproduce pressurized crack patterns in quasi-brittle media, providing a consistent and computationally effective approach for future multiscale analyses.
Abstract To investigate the mechanical behavior of frozen soil subjected to shaped charge jet penetration at different temperatures, a combined theoretical and experimental approach was adopted. In the theoretical part, based on the dynamic cavity expansion model, the dynamic penetration resistance of frozen soil at various temperatures under high-velocity shaped charge jet penetration was calculated by incorporating the constitutive model and equation of state (EOS) for frozen soil. The calculated dynamic penetration resistance was then integrated with the axial penetration model of the shaped charge jet and the radial cavity growth model to determine the penetration cavity profile formed by jet penetration into frozen soil at different temperatures. The dynamic penetration resistance was subsequently validated through experiments on shaped charge jet penetration into frozen soil at −6 °C. The results indicated that as temperature decreases, the dynamic penetration resistance of frozen soil increases significantly, while the cavity diameter decreases markedly. However, no obvious variation was observed in cavity depth.
Abstract This study presents a stage-wise sectional analytical model for reinforced concrete (RC) beams strengthened with carbon textile-reinforced concrete (TRC) under sustained loading. The formulation accounts for pre-cracking, partial unloading, residual curvature, and TRC activation under non-zero initial strain. The TRC layer is modeled with bilinear tensile behavior, while tension stiffening and residual tensile effects of cracked concrete are included. The model is validated using full-scale bridge beams after about 30 years of service, tested under realistic conditions. The strengthened beam shows an increase of about 25% in ultimate load and improved crack control, with crack width and spacing reduced to one-third to one-half of the control beam. Strain results confirm effective stress redistribution and high textile utilization. Predictions agree well with experiments, with discrepancies within 5–10%. Compared with design guidelines, Z-31.10-182 is closest, while ACI 549.4R-20 and CNR-DT 215/2018 overestimate capacity. The model provides a reliable framework for assessing TRC-strengthened RC members under realistic conditions.
Abstract Conventional steel strand anchorages are unsuitable for fiber-reinforced polymer (FRP) materials. This study evaluates a new bond-type anchorage system for unbonded post-tensioned GFRP bars. Prestressing is applied through a steel strand housed within a component threaded onto an adapter connected to the live-end anchorage. Two concrete beams reinforced with two post-tensioned GFRP bars were tested. The bars in Beam 1 were prestressed to 45.1% of their guaranteed tensile strength, and those in Beam 2 to 27.5%. Concrete strains were monitored during and after prestressing, followed by four-point bending tests. The system effectively transferred the prestressing force with minimal losses and no slippage. Beam 1 exhibited a 13.7% immediate strain loss after the second bar was prestressed. Beam 2 was prestressed two times, with average losses of 6.4% and 15.6% on each side after the first bar was prestressed, and 5.0% and 8.0% after the second. After these immediate losses, the prestressing force remained stable. The anchorages performed effectively under bending, maintaining GFRP bars prestress even after concrete crushing.
Abstract A simple way to obtain numerically the lateral load capacity curve of a masonry wall is to consider it as a one-dimensional element and perform a finite element incremental analysis. Based on some assumptions concerning the normal stress distribution, the panel can be discretized into frame elements whose geometrical properties are evaluated from the portion of the cross-section subjected to compression. In the case of employing finite elements of constant cross-sections, satisfactory results are obtained only if the mesh is dense enough to accurately represent the change in the geometrical properties of the resisting portion of the panel cross-section. In this work, a finite element with a variable cross-section is employed, so the number of elements required for a reliable solution can be reduced. The proposed model is tested against some experimental results available in the literature. Results are in good agreement with reference curves, showing that the proposed model may be employed to assess the load capacity of masonry shear walls in a pre-design phase.
Abstract This study introduces, for the first time, a high-order three-dimensional quadrature element for the coupled membrane and bending analysis of plate and beam structures under static and free vibration conditions. The formulation combines high-order polynomial interpolation with quadrature-based numerical integration to accurately represent three-dimensional stress and displacement fields. Unlike conventional two-dimensional approaches, the proposed model accounts for through-thickness deformation, making it suitable for both thin and thick structures. Consistent formulations are developed for in-plane and out-of-plane behaviors, with natural coupling achieved within a unified 3D framework. Numerical examples demonstrate the accuracy, efficiency, and robustness of the element in handling complex boundary conditions and higher vibration modes for isotropic and functionally graded materials. The results show rapid convergence, strong agreement with reference solutions, and reliable prediction of natural frequencies. This work provides an effective tool for high-fidelity structural analysis using three-dimensional finite elements.
The design optimization of Annular Shaped Charge (ASC) is highly complex and nonlinear. Traditional ASC optimization focuses on liner structure using empirical methods, while optimization for annular charges is scarce because slight charge variations significantly alter the annular penetrator morphology. To address this, we propose a predictive model for Optimal Charge Compensation Amount (OCCA) of Hollow Annular Shaped Charge (HASC) by integrating Finite Element Method with Multilayer Perceptron (FEM-MLP). Through dimensional analysis and theoretical calculations, we identified four input parameters. Using these, 1431 data points were generated to train and test the MLP. Compared with SVR, Random Forest, and Linear Regression using 5-fold cross-validation, the MLP showed superior prediction accuracy and generalization. The trained MLP predicted OCCA for random and experimental structures, and numerical simulations confirmed high accuracy and generalization. The charge compensation method is broadly applicable for similar HASC structures. The optimized annular jet exhibits no deviation and delayed fracture, providing insights for annular jet penetration into targets.
This study presents a nonlinear dynamic analysis of functionally graded half-cylinder sandwich (FGhCS) shells with elastic boundary conditions (EBCs) subjected to explosive loading (EL). An efficient finite element framework is developed based on a novel first-order shear deformation theory (n-FSDT) to account for both geometric and material nonlinearities. The governing equations are systematically derived from Hamilton's principle, incorporating large deformation effects through von K & aacute;rm & aacute;n-type kinematics. The proposed model is validated against benchmark solutions, demonstrating high accuracy and improved computational efficiency. Parametric investigations are performed to assess the influences of geometric characteristics, material gradation, and boundary stiffness on the dynamic response. The results reveal that appropriate material distribution and elastic restraints can effectively mitigate the adverse effects of explosive loads, providing valuable insights for the optimal design of sandwich shell structures.
This study investigates the down-aisle seismic performance of a full-scale 3D cold-formed steel rack system using shaking table tests. The rack system was tested using scaled Northridge earthquake records, and the dynamic responses were evaluated during the test. The results demonstrated that the rack response remained essentially elastic up to approximately 50% of the Northridge intensity, beyond which pronounced inelastic behavior, approximately 50% stiffness degradation, and permanent drifts were observed. The experimental results were validated using an FE analysis, with substantial agreement in the elastic-to-mildly inelastic range, with similarity ratios of approximately 80%. However, differences were observed in the response values at the higher excitation intensities due to the high pallet sliding and connection slip during the test, which could not be accurately reflected in the FE model. It was observed that pallet sliding and connection friction, rather than member strength alone, governed the response under strong shaking and should be explicitly considered in advanced numerical models and in the seismic assessment of steel racks.
The experimental study investigates design parameters affecting the fatigue performance of bolted flange connections using accelerated laboratory tests at 60-70% of static capacity. Constant-amplitude loading R = 2 Hz was applied to large-diameter high-strength bolts (M36 and M39, Grade 8.8), considering variations in flange material S355 and SAE 1045, bolt size, and loading 5 mm eccentricity. M39 bolts showed statistically significant longer fatigue life than M36 bolts 8,579 vs. 5,395 cycles, p = 0.023. A 5 mm loading eccentricity reduced fatigue performance due to induced bending effects. While both flange materials showed comparable fatigue lives, the higher ductility of S355 provided improved damage progression control. Dynamic stiffness monitoring identified a three-stage degradation process, with critical reductions in final fatigue stages, indicating potential for early failure detection. Although accelerated tests do not predict absolute service life, results provide relative performance rankings and practical guidance for bolt selection and design of large-scale bolted structures, particularly wind turbine towers.
The aging state and operational environment of lithium-ion batteries (LIBs) in electric vehicles are highly complex and variable. To investigate LIB safety under foreign object collisions, this study develops a detailed finite element model of 18650 LIBs at different cycle counts. Following model validation, we conduct comprehensive simulation tests using indenters of varying types, sizes, intrusion angles, and loading positions. A machine learning model is subsequently developed to rapidly predict battery failure displacement and load. Results demonstrate that this approach achieves high-accuracy prediction of LIB failure behavior, providing a valuable reference for other LIB application scenarios.
Accurate prediction of occupant injury responses is essential for the effective design and optimization of vehicle occupant restraint systems (ORS). To address the complexity and time-consuming nature of injury prediction in existing occupant restraint system (ORS) design workflows, this study proposes a deep learning-based method tailored for frontal collision scenarios. The proposed method enables rapid injury prediction by simultaneously processing crash waveform signals and ORS parameters as inputs. It enables accurate prediction of time-dependent biomechanical response curves across multiple occupant body regions, effectively capturing the complex, nonlinear interactions between dynamic impact conditions and restraint system characteristics. The proposed method requires only 2.7 seconds to predict the occupant's head acceleration-time curve and thorax compression-time curve, as well as to compute the corresponding injury assessment indicators (C-NCAP 2024). The predicted curves achieve a similarity score of over 0.86, and the accuracy of the selected injury assessment indicators exceeds 0.80. Compared with multi-rigid body simulations, the computational efficiency is improved by 533 times. These results demonstrate the model's potential for intelligent, data-driven, and time-efficient ORS design.
This study presents an experimental-numerical investigation on one-way geopolymer concrete (GPC) slab strips internally reinforced with steel or GFRP bars and externally strengthened using a glass fabric-reinforced cementitious matrix (FRCM) system. Six full-scale specimens were tested under four-point bending to characterize cracking response, stiffness evolution, strengthening efficiency, and governing failure mechanisms. The steel-reinforced control slab exhibited a ductile flexure-controlled failure. With glass-FRCM strengthening, the ultimate load increased by approximately 31% for one layer and 59% for two layers, accompanied by improved crack distribution and enhanced post-cracking stiffness, while maintaining flexural dominance. In contrast, the GFRP-reinforced control slab failed in shear, highlighting the limited stress redistribution associated with the lower elastic modulus and linear-elastic behavior of GFRP bars. Glass-FRCM strengthening improved tensile stiffness and crack control; however, the strengthened GFRP slabs remained shear-governed, indicating that flexural strengthening alone may be insufficient to prevent premature diagonal cracking. Overall, the results demonstrate that strengthening effectiveness is strongly dependent on the internal reinforcement type, and that additional shear strengthening measures are required for GFRP-reinforced GPC slab systems.
To investigate the effect of variations in priming output pressure characteristics on action time in chamber and maximum chamber pressure. A collaborative test method of primer output-internal ballistics was proposed. Designed primer output test device and internal ballistic performance test device. Aiming at the six factors, experimental study was carried out using the control variable method, respectively. Analyzing the contribution of each influencing factor to internal ballistic performance parameters using principal component regression analysis. Results indicate that shortened pressure start time and pressure peak time of primer output, reduced action time in chamber of the internal ballistics. And within a certain range, when pressure peak of primer output decreased, maximum chamber pressure decreased and action time in chamber of internal ballistics prolonged. High impact of dose of priming composition, damp of primer and ambient temperature on internal ballistic performance. Mapping relationship between output pressure characteristics of primer and internal ballistic performance of bullet was established.
To support the safe and efficient utilization of coal gangue (CG) as aggregate in underground support structures, this study systematically investigates the dynamic fracture response and damage evolution of coal gangue concrete (CGC) under single and cyclic impact loading. Experimental results show that increasing the CG replacement ratio reduces dynamic strength and elastic modulus while raising peak strain. Under cyclic impact, the impact resistance life shortens significantly, and damage evolution follows a "weak-phase-dominated" mechanism driven by the low strength of CG aggregates and weak interfacial zones. As the replacement ratio increases, failure transitions toward a crushing-dominated mode governed by aggregate fracture and interfacial slip. Based on these findings, a dynamic strength degradation model coupling the replacement ratio and impact number is established to predict residual load-bearing capacity after cyclic impact. This work provides a theoretical basis for the design and safety assessment of CG concrete structures in dynamically disturbed underground environments.
This paper presents a precast concrete composite slab-steel truss formwork system incorporating demountable joints to achieve composite behavior between the upper slab and the lower truss, thereby facilitating truss reuse. The system enables shoring-free construction for medium to long spans(3.0m<^>6.0m), enhancing construction efficiency and reducing material consumption. To assess its performance under realistic conditions, three full-scale specimens were subjected to vertical static bending tests involving a loading-unloading procedure. A finite-element model was developed and calibrated against experimental results, followed by a parametric analysis. The system demonstrated excellent flexural performance with minimal residual deformations after unloading, indicating high recoverability and reliable reusability. Parametric studies reveal that increasing slab thickness primarily enhances the slab's behavior with negligible influence on the global structural response, whereas truss height and member cross-sections predominantly govern overall stiffness and load-bearing capacity. Based on experimental and numerical findings, simplified design equations for strength and deflection are proposed to support design optimization and practical implementation.
